[jerf]

"Assuming all possible inputs to the compiler cause it to halt."

If the compiler did not halt, then we don't have anything to disassemble in the first place.

Formally, it is obvious that a diagonalization-based search will eventually find a correct input, regardless of the halting status of any given input. In practice, none of this matters very much.

[burgerbrain]

As I explained in my other comment, the compiler certainly does halt for the correct input, but that does not mean it will halt for all inputs.

You are however correct that this can be circumvented with diagonalization.